Gas Cloud Will Collide with our Galaxy’s Black Hole in 2013

byNancy AtkinsononJune 26, 2012

Scientists have determined a giant gas cloud is on a collision course with the black hole in the center of our galaxy, and the two will be close enough by mid-2013 to provide a unique opportunity to observe how a super massive black hole sucks in material, in real time. This will give astronomers more information on how matter behaves near a black hole.

“The next few years will be really fantastic and exciting because we are probing new territory,” said Reinhard Genzel, leading a team from the ESO in observations with the Very Large Telescope. “Here this cloud comes in gets disrupted and now it will begin to interact with the hot gas right around the black hole. We have never seen this before.”
By June of 2013, the gas cloud is expected to be just 36 light-hours (equivalent to 40,000,000,000 km) away from our galaxy’s black hole, which is extremely close in astronomical terms.

Astronomers have determined the speed of the gas cloud has increased, doubling over the past seven years, and is now reaching more than 8 million km per hour. The cloud is estimated to be three times the mass of Earth and the density of the cloud is much higher than that of the hot gas surrounding black hole. But the black hole has a tremendous gravitational force, and so the gas cloud will fall into the direction of the black hole, be elongated and stretched and look like spaghetti, said Stefan Gillessen, astrophysicist at the Max Planck Institute for Extraterrestrial Physics in Munich, Germany, who has been observing our galaxy’s black hole, known as Sagittarius A* (or Sgr A*), for 20 years.

“So far there were only two stars that came that close to Sagittarius A*,” Gillessen said. “They passed unharmed, but this time will be different: the gas cloud will be completely ripped apart by the tidal forces of the black hole.”

Watch a video of observations of the cloud for the past 10 years:

No one really knows how the collision will unfold, but the cloud’s edges have already started to shred and it is expected to break up completely over the coming months. As the time of actual collision approaches, the cloud is expected to get much hotter and will probably start to emit X-rays as a result of the interaction with the black hole.

Although direct observations of black holes are impossible, as they do not emit light or matter, astronomers can identify a black hole indirectly due to the gravitational forces observed in their vicinity.

A black hole is what remains after a super massive star dies. When the “fuel” of a star runs low, it will first swell and then collapse to a dense core. If this remnant core has more than three times the mass of our Sun, it will transform to a black hole. So-called super massive black holes are the largest type of black holes, as their mass equals hundreds of thousands to a billion times the mass of our Sun.

Black holes are thought to be at the center of all galaxies, but their origin is not fully understood and astrophysicists can only speculate as to what happens inside them. And so this upcoming collision just 27,000 light years away will likely provide new insights on the behavior of black holes.

Lead image caption: Images taken over the last decade using the NACO instrument on ESO’s Very Large Telescope show the motion of a cloud of gas that is falling towards the supermassive black hole at the centre of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. Credit: ESO/MPE

Nancy Atkinson is currently Universe Today's Contributing Editor. Previously she served as UT's Senior Editor and lead writer, and has worked with Astronomy Cast and 365 Days of Astronomy. Nancy is also a NASA/JPL Solar System Ambassador.

I have the odd feeling of having said that before, but I am so much looking forward for all the data coming in. It might not be the fireworks of a fully armed and operational battle… äh, active galactic nuclei (AGN). However, it will be fairly close to one, and the best we’ll probably ever get. There’s going to be so much to be learned from this event.

All telescopes on alert. Standing by to observe the final destruction of the rebel…. äh, you know…

No – of course by “collision” I don’t mean something crossing an event horizon!
I believe collision refers to physical contact and an exchange of forces.
I believe the word is being improperly applied here.

This is *science*, after all!

If this author used “smashes into” instead of “collides”, I think you’ll see my point.

But crossing the event horizon (or also just flying by) is also a collision in your definition, that is an exchange of forces – exchange of gravitational force.

In physics anything where something is deflected from its straight trajectory by something else is called a “collision”. The word is actually correctly applied here.
As squidgeny below stated correctly, on atomic scales and below, you do not have physical contact between particles – just an exchange of electromagnetic “forces”. And believe it or not, to be absolutely correct, even on our own scales any collision is in the end the exchange of electromagnetic forces (and also a consequence of Pauli’s exclusion principle… but that’s a story on its own 😉 ).

[…], on atomic scales and below, you do not have physical contact between particles – just an exchange of electromagnetic “forces”. And believe it or not, to be absolutely correct, even on our own scales any collision is in the end the exchange of electromagnetic forces […].

I think you’ll have a hard time trying to explain that to the firemen who have to hose down the sidewalk after someone did a ‘Peter Pan’ off the Empire State Building! 😉

It’s one of those words that makes perfect sense at the scale of our every-day existence, but down at the atomic level the concept of things “touching” starts to break down, and I suppose that same exception can go for black holes

One problem, and it really has nothing to do with the collision and the physics we’ll get from it, but supermassive black holes are not formed by the collapse of a supernova. No stable star could be large enough to form the black hole at the center of the galaxy.

Contrary to popular thought, it is actually hard to get something into a black hole. This gas cloud will for the most part pass by the black hole with most of the gas deflected onto a different trajectory. The gas cloud will distend into an elongated shape with only a small percentage of this material that makes a sufficiently close approach entering the black hole. The angle with which each atom is deflected depends upon the distance d if approaches the gravitating body. If a straight line is drawn along the direction a particle approaches the black hole (or gravitating body) the closest distance d is the impact parameter. For v the velocity of the particle far away from and U(r) = -GM/r the gravitation potential one can show that the angle of deflection is

? = ? – 2d ?_r^? dr/(r^2 sqrt{1 – (d/r)^2 – 2U(r)/mv^2}),

where as the impact distance decreases the angle of scatter increases.

Largely this material will then evolve from being a roughly spherical appearing distribution into a spreading and increasingly elongated cloud. What we may observe is some radiation released from material heating of the cloud during this process. Some dissipation may cause material to enter into orbit or an accretion disk around the black hole. These observations will indicate how the kinetic energy of a gas cloud is converted into radiation or heat, and how the material changes its configuration.

It is a bit of a problem trying to figure out large black holes form to begin with. It is not hard to see how a stellar mass black hole forms by implosion. The big question is then how does a 10 solar mass black hole evolve in time into a multi-million or even more a multi-billion solar masses black hole. It seems tough to figure out a black hole can over a few billion years evolve into the behemoths we observe. Even some of the UT blog articles here indicate how black holes are “grazers not gulpers” and so forth. I would bet that at most a few percent of this gas cloud actually ends up in the black hole, with a good change that almost none of it actually gets absorbed by the black hole.
LC

IIRC, in a previous UT article of this topic there was a short movie of a simulation the ESO scientists already performed. I think, it showed that some parts of the cloud actually enter in an orbit while the rest is deflected elsewhere. (Not to mention that it would be highly disappointing not to get the tiniest bit of accretion out of it 😉 .)

It seems tough to figure out a black hole can over a few billion years evolve into the behemoths we observe.

It gets even more mysterious, if one considers the fact that we observe these monsters already a few hundred million years after the BB. A few years ago I attended a talk where someone made the proposal that self-gravitating discs could aid the process of feeding black holes to that mass in a short enough amount of time. I haven’t heard anything new from that since then, but I also don’t follow the literature that much on this topic.

I too have heard of this idea about self gravitating tori or disks. It is the case that evidence for SMBHs a billion years or so after the BB is fairly clear.

The other side of the conundrum is that intermediate mass black holes are fairly rare. A few have been found in the 10^2 and 10^3 solar mass range. However we would tend to expect a fair number of growing black holes in those early billion years to have stopped growing prematurely, so there should be a number of these intermediate mass black holes in our galaxy. Maybe they are rogue black holes inside or outside of galaxies.

Now THAT is one amazing zoom – RIGHT to the heart of the matter! (He snickers)
WHERE did that ‘cloud’ come from? Residual gas left over from the formation of the Milky Way? Or perhaps the Milky Way is shown here in the process of capturing the gas from a colliding dwarf galaxy? Or perhaps our galaxy’s Black Hole is capturing another BH?

Then, from way far out there in left field: Were that this cloud be made of anti matter or even mirror matter(?)… then we’d see some firey works! No? ~@; )

Actually we did. I don’t have an example at hand, but that’s the way to detect most of the quiet black holes that are not actively feeding. The process is called micro lensing (just a small gravitational lens).